you generally want to purchase the sharpest lens you can afford. i would go with the 55-250 if they are similarly priced, or within your budget. the new 18-55's are pretty darn good, and it'll be what you carry around with you when shooting indoors, portraits, or general shooting. if you're going to shoot outdoors, you'll appreciate the added reach with the 250, but you'll also want a tripod or monopod (at full zoom, it'll be difficult to get sharp shots while going handheld).
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